Richard E. Smalley, Robert F. Curl, Jr., and Harold W. Kroto
Richard Smalley with a model of a buckyball. Photo by Tommy LaVergne, University Photographer, Rice University. Used with permission.
With their discovery of buckyballs in 1985, Richard E. Smalley (1943–2005), Robert F. Curl (b. 1933), and Harold W. Kroto (1939–2016) furthered progress to the long-held objective of molecular-scale electronics and other nanotechnologies. Molecular-scale electronics, or molecular electronics, is the ongoing effort to use individual molecules to perform functions in electronic circuitry. With transistors the size of single molecules, for example, electronic devices could become dramatically smaller than today’s microelectronics devices. Molecular electronics is a subfield of nanotechnology, the broader effort to view, measure, and manipulate materials at the molecular or atomic scale, prophesied by Richard Feynman in 1959.
Yet molecular electronics and nanotechnology were not part of the immediate research agendas of Smalley, Curl, and Kroto in 1985, when the three chemists gathered for 10 days at Rice University in Houston, Texas. Rice was Smalley’s and Curl’s home university, and Kroto was a chemist at the University of Sussex in England. All three chemists were spectroscopists who spent their time probing phenomena at the atomic and molecular level with advanced spectrometers.
Harold Kroto in 2000 at the Chemical Heritage Foundation, Philadelphia. CHF Collections. Photograph by Douglas A. Lockard.
Kroto had been using a special type of spectroscopy (microwave spectroscopy) to study long carbon chains found in space. He hypothesized that such chains had been created in the atmospheres of carbon-rich red giant stars, and he wanted to use a piece of equipment invented by Smalley in order to investigate this hypothesis. Smalley’s laser-generated supersonic cluster beam apparatus (AP2 in laboratory parlance) fired pulsed laser beams at chemical elements, achieving temperatures hotter than the surface of most stars and vaporizing the target element. As the vapor began to cool, the evaporated atoms would align in clusters.1 A high-pressure burst of gas would then sweep the vapor into a vacuum chamber, where the clusters condensed as the vapor cooled. A second laser pulse ionized the clusters, pushing them into a mass spectrometer, where they could be analyzed. Kroto wanted to aim the AP2’s lasers at carbon to recreate the high-heat conditions of a red giant’s atmosphere and study the clusters of carbon thus produced.
Robert Curl in 2009 at the Chemical Heritage Foundation, Philadelphia. CHF Collections.
When first approached by Kroto in 1984, Smalley was reluctant to interrupt the cluster research he and Curl were doing on metals and semiconductors to make his device available to Kroto. But he and Curl ultimately conceded, and Kroto arrived at Rice University on September 1, 1985. The first results of their carbon experiments, conducted with the essential aid of graduate students James Heath, Sean O’Brien, and Yuan Liu, were in fact the long carbon snakes that Kroto had sought. Next the students noted an unusual peak in the mass spectra of the clusters formed by the AP2, showing the presence of an abundance of molecules composed of 60 carbon atoms (C60). Such an abundance suggested the stability of this macromolecule. What was it?
Now with the three senior scientists fully engaged, the researchers intensively puzzled over what the structure of such a macromolecule must be. Perhaps it was composed of stacks of hexagonal sheets of carbon, like graphite, but with all the dangling bonds tied up in some fashion, or a spherical form where the hexagonal graphite sheet curled around and closed. But solid geometry did not permit such a regular solid. One night Smalley resorted to the method of scissors and tape and inserted some pentagons in the structure, prompted by Kroto’s recollection earlier that day of having once made a paper star dome for his children that included pentagons as well as hexagons. Smalley’s result was a polygon with 60 vertices and 32 faces, 12 of which are pentagons and 20 are hexagons. The scientists named their macromolecule buckminsterfullerene, after the American architect, R. Buckminster Fuller, who had designed similarly constructed geodesic domes. The nickname “buckyball” soon stuck, because it resembled a soccer ball.
Finding a new, highly stable form of a pure element is rare in the world of chemistry, and for this reason alone the discovery of buckyballs was noteworthy. But it also opened up a whole new field of chemical study with practical applications that scientists are only beginning to uncover. Buckyballs were the first of a whole class of hollow, closed-shell carbon macromolecules that came to be known as fullerenes. They have become the subject of intense research, both for their unique chemistry and for their technological applications, especially in materials science, electronics, and nanotechnology.
Perhaps the most significant fullerenes to emerge since the buckyball are carbon nanotubes, or “buckytubes,” discovered in 1991 by Iijima Sumio of NEC Corporation in Tsukuba, Japan. A buckytube is a carbon sheet rolled into the shape of a tube or cylinder, capped with round domelike ends, and with a diameter of approximately a single nanometer, or one-billionth of a meter, but extremely long by comparison. These long, thin tubes opened up further research by Smalley and others in fullerenes and their applications. Since then, thousands of new compounds have been synthesized with non-carbon atoms incorporated in fullerenes, sometimes actually caged inside them. Nanotubes exhibit promising characteristics for various applications. They are excellent conductors of heat and of electricity, exhibit novel electrical properties, possess extreme tensile strength, and are able to penetrate membranes such as cell walls. Applications in electronics, structural materials, and medicine beckon. In 2006 IBM researchers succeeded in building the first electronic integrated circuit around a single carbon nanotube, heralding further advances in molecular electronics. Among the “moletronics” applications currently available to the consumer are carbon-nanotube-based LED (light-emitting diode) displays.
Curl is a native Texan, born in the small town of Alice to a Methodist minister and administrator. His family moved frequently among Texas towns and cities. Like many a chemist, Curl first became interested in his subject when his parents presented him with a chemistry set. A high school teacher cultivated his interest by creating just for him a second year of chemical studies beyond the standard one-year course. Curl earned his bachelor’s degree at Rice and proceeded to the University of California, Berkeley, for a Ph.D. in physical chemistry and Harvard University for postdoctoral studies. In 1958 he returned to Rice as a faculty member and spent of the rest of his academic career there. Curl’s fine work in laser spectroscopy convinced Smalley to take his first faculty appointment at Rice.
Smalley was a Midwesterner, born in Akron, Ohio, and raised in Kansas City, Missouri. His father, a successful publisher of agricultural trade journals, worked with his son in their basement shop, building things and fixing mechanical and electrical equipment—good background for a future inventor of scientific instruments. It was Smalley’s mother who inspired her youngest son with a love of science. She had returned to college after having given birth to four children and enjoyed discussing with the boy what she was learning. In addition, Smalley’s aunt, Dr. Sara Jane Rhoads, a professor of chemistry at the University of Wyoming, served as a great example, and even gave Smalley summer employment in her laboratory. He began his undergraduate studies in chemistry at Hope College in Holland, Michigan, and finished at the University of Michigan, Ann Arbor. Rather than going directly to graduate school, Smalley spent time working at the Shell Chemical Company’s polypropylene plant and technical center in Woodbury, New Jersey. After four years with Shell, he enrolled in doctoral studies in Princeton University’s chemistry department. He capped off these studies with postdoctoral research at the University of Chicago. It was there that he pioneered supersonic jet laser beam spectroscopy. Smalley came to Rice in 1976 with the intention of collaborating with Curl.
In 1937 Kroto’s parents fled from Berlin to London because his father was Jewish and the Nazi laws against Jews foretold worse persecution to come. Kroto was born in 1939 in the small town of Wisbech in England, to which his mother was evacuated because of the blitz of London by the German air force. Meanwhile his father was interned on the Isle of Man as an enemy alien, ironically because he detested the Nazis. When he was still a baby, Kroto and his mother moved to Bolton, where they were eventually joined by his father. Soon after the war his father was able to set up a small factory making and printing balloons, in which Kroto worked as a teenager during school vacations. At Bolton School, Kroto enjoyed art and graphic design, but his chemistry teachers instilled in him a special affection for that discipline. On their advice he attended Sheffield University. As an undergraduate, while earning his B.S. in chemistry, he participated enthusiastically in student activities as art editor of the student magazine, secretary of the tennis team, and president of the athletics council. He continued at Sheffield for his Ph.D. in molecular spectroscopy. Eager to work abroad, he conducted postdoctoral studies at the Canadian National Research Council in Ottawa and at Bell Labs in New Jersey. In 1967 he returned to Sussex and held faculty appointments there until 2004.
In 1996 Smalley, Curl, and Kroto shared the Nobel Prize in chemistry for their discovery of fullerenes. Earlier that same year Kroto was knighted by Queen Elizabeth. Curl is now an emeritus professor, but he continues to be associated with Rice University’s Laser Science Group and the Richard E. Smalley Institute for Nanoscale Science and Technology. In 2005 Smalley lost his long battle with leukemia, and this institute that he had founded in 1993 was renamed in his honor. After his early work on buckyballs and nanotubes, Smalley investigated processes which could be scaled up for commercial production, and in 2000 founded Carbon Nanotechnologies Inc. (acquired by Unidym in 2007). He also became a public advocate for federal support of nanotechnology initiatives in the United States and for solutions to the world’s energy problems. Kroto, too, used his scientific fame to gain greater public attention for science. In 1995 he set up the nonprofit Vega Science Trust with BBC producer, Patrick Reams, with the objective of creating high-quality science films for broadcast and the Internet. After retiring from Sussex, he became a professor at Florida State University in Tallahassee to pursue scientific research and further his international educational projects.
1. A cluster is a complicated chemical and physical concept. Simply speaking, it is an aggregate or assembly of atoms with properties, including size, intermediate between those of a molecule and a bulk solid. A buckyball is a cluster of 60 carbon atoms. For the purposes of the remainder of this essay, a cluster is considered akin to a large molecule, or macromolecule.